The success and proliferation of microfluidics research has spawned significant interest in nanofluidics research as techniques for nanofabrication are advanced and becoming more widespread. Nanofluidics research encompasses a very broad range of topics from chemistry to biology to physics; the promise of answers to fundamental questions in each is the goal. Some of the research being pursued includes the fundamental properties of liquids and the separation or sorting of molecules based on size and charge. Furthermore, there is considerable interest in the controlled confinement and manipulation of single polymeric or bio-molecules (e.g., DNA) for analysis. The current methods for fabricating nanochannels for molecular confinement generally consist of multiple rather complicated steps involving costly equipment. Additionally, most of these methods produce static nanochannels, where the cross-sectional dimensions cannot be changed during an experiment.
Currently, nanochannels are generally produced with standard microfabrication techniques. In substrates of silicon, SiO2, or silicon nitride, lithographic techniques such as electron-beam lithography or nano-imprint lithography and reactive ion etching (Fu et al., Nature Nanotechnology 2, 121 (2007)) are used to create raised patterns of networks of channels. Non-lithographic approaches include focused ion beam milling or the patterning of sacrificial layers. After a pattern has been created, frequently a bonding step is required. The use of high temperature and pressure techniques, like anodic bonding, is not uncommon. Elastomeric materials permit the employment of the easier and cheaper soft lithography techniques for creating nanochannels (Huh et al., Nat. Mater. 6, 424 (2007)). Other methods include a method for creating open channels by which a diluted PDMS mixture is directionally swiped onto a glass slide using lint-free towelettes for very small (3 nm×160 nm) nanochannels (Muller-Buschbaum et al., Appl. Phys. Lett. 88, (2006)). In borrowing from the communications industry, a method analogous to that of drawing optical fibers was used to thermally draw-down a polycarbonate millimeter-sized rectangular cross-section containing initial 30-μm sized microchannels ending up with approximately 700 nm-diameter nanochannels (Sivanesan et al., Anal. Chem. 77, 2252 (2005)).
What is needed in the art are simple and robust compositions and methods for performing nanoscale biological assays.